Ultra short wave receiver



B. TREVOR ULTRA SHORT WAVE RECEIVER Original Filed May 19, 1936 4 Sheets-Sheet 1 PRIMARY FILTER INVENTOR BERTRAM TREVOR 1 fl $411M,

ATTORNEY June 24, 1941.. B. TREVOR ULTRA SHORT WAVE RECEIVER Original Filed May 19, 1936 4 Sheets-Sheet 2 H601 Fi .2 H63 F7614 I F: AMPL lF/ER INVENTOR BER RAM TREVOR BY 83 ATTORNEY l-WQM F152 Elm E1,

B. TREVOR ULTRA SHORT WAVE RECEIVER Original Filed May 19, 1936 4 Sheets-Sheet '3 AMPL. 0E7:

AUDIO 0" PUSH BUTTON I F All/[PL lF/ER INVENTOR BERTRAM TREVOR ATTORNEY June 24, W41. 4 B. TREVOR 2,247,213

ULTRA SHORT WAVE RECEIVER Original Filed May 19, 1936 4 Sheets-Sheet 4 -48mh. b r0 U77L/ZA7770/V MEANS T,2mf J T p F a e a 1 i g. m T\ 100.0. E J & A 1//. .006m LL MANUAL fi 5/wm 4.6.6.

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INVENTOR BERT RAM TREVOR 24 ava-M,

ATTORNEY Patented June 24, lg il rss ears "ULTRA SHORT WAVE RECEIVER of Delaware Qriginal application May 19, 1936, Serial No.

1940, Serial No. 323,718

(Cl. 25( 2fi) 13 Claims.

This invention relates to ultra short radio wave systems, and is a division of my copending application Serial No. 80,492, filed May 19, 1936, now United States Patent No. 2,202,035, granted May 23, 1940.

One of the objects of the present invention is to provide an ultra short wave receiver capable of receiving an extremely wide modulation band, such as might be used in the transmission of television programs. Such a modulation band may be of the order of about three million cycles. A further object is to provide a band pass transformer having balanced primary and secondary circuits of the coaxial line type.

In accordance with the invention, there is employed a novel type of band pass transformer for passing the energy received by the antenna to a balanced detector circuit, to which are fed locally generated high frequency oscillations from a resonant line controlled oscillator. The output of the detector is designed to feed into a cascaded intermediate frequency amplifier which, in turn, may be coupled to a second detector circuit from which the output is amplified and arranged to pass into a suitable utilization circuit.

Various features of the present invention relate to (l) a novel coaxial or concentric line type of band pass transformer, (2) the concentric frequency control line for the local oscillator, and (3) the automatic gain control circuit. Although these features are hereinafter described with particular reference to a receiver circuit, it should be understood that they are not limited thereto, since they are capable of being used in other systems.

Other objects and features, and their advantages will appear more fully hereinafter in connection with the accompanying drawings, Figs. 1, 2, 3 and l of which, taken together, illustrate a complete receiving circuit for receiving ultra short waves of the order of 1.7 meters, although it is to be understood that the invention is not limited'to this particular wavelength. Fig. is a box diagram indicating how Figs. 1, 2, 3 and 4 should be combined to complete the receiver circuit. Fig. la is a cross-sectional view of the coaxial line transformer of Fig. 1 along the lines la-Ia.

Referring to the drawings in detail, there is shown in Fig. l a band pass transformer comprising a plurality of pairs of coaxial or concentric lines I, 2; I, 3H1, 5; and l, t. It will be noted that there are two pairs of lines oppositely and symmetrically located with respect to a central metallic plate 7, and that the conductors on one Divided and this application March 13,

side of plate I are extensions, or on the same straight line with the conductors on the other side of the plate. Since the coaxial lines on each side of the central metallic plate I are located next to one another, it is proposed, for purposes 'of convenience and design, to employ a common outer conductor for both pairs of lines on the same side of the center plate and to accomplish this result the outer conductors are made to have a square form, as shown in Fig. 1a, which is a cross-sectional View of the band pass transformer along the line ia-ia. The outer conductors i and t are made of seamless, square, brass or copper tubing and are arranged to be symmetrically positioned with respect to their associated inner conductors. These square tubings are designed to extend beyond the ends of the inner conductors and to be closed at such ends in order to completely shield the entire system. The inner conductors 2, 3; and 5, B are joined together at their ends by means of variably balanced condensers C2, C2. Each half of the band pass transformer, looked upon from the center toward the ends, is a resonant circuit completely balanced with respect to ground. Both resonant circuits comprising halves l, 2 l, 3; and 4, 5; 4, 6 are coupled together at their inner conductors by means of connections 8 and 9 which couple together the inner conductors extending on the same straight line, preferably substantially symmetrically with respect to the center plate I, as shown. It will thus be seen that We have the equivalent of a transformer comprising two balanced resonant circuits coupled together, each resonant circuit being equivalent, electrically, to a parallel tuned circuit. A damping resistance R, of the correct value, is shown connected across the adjacent ends of the inner conductors of one of the balanced tuned circuits in order to assist in obtaining the desired flat top characteristic of the transformer; that is, so that both balanced halves l, 5; l, 6; and l, 2; i, 3; may effect a band pass transformer. In certain instances it may be desirable to provide an additional damping resistance across the opposite adjacent ends of the inner conductors of the other tuned resonant circuit, although this is not necessary in the present case. The band pass transformer, just described, is coupled to a suitable input circuit, herein designated the antenna, through a pair of connections H] which are conductively joined to the inner conductors 2, 3 of one-half of the band pass transformer. This last balanced circuit comprising i, 2; I, 3 will thus be designated the primary of the transin push-pull (i. e., the signal waves are applied to the grids out of phase with respectto each other), while the local oscillations generated by oscillator M are applied to the cathodes of the tubes l2, 13 in push-pull (i. e., in parallel rela-. tionship). In the output of-thedetector-tubes l2, 13 there is a transformer LcL4 whose primary winding L3 is balanced with respect to ground but whose secondary winding L4 is unbalanced with respect to ground and coupled to the intermediate frequencyamplifier. A balanced condition of the primarywinding L3 is maintained by the electrostatic shield ld which symmetrically-- surrounds the COflw A portion ofthls-shield is positioned betweenLz and L4. It shouldbe noted that windings-1c and- L4 comprisea band pass transformer for passing'the desired wide'moolulation band on to the-intermediate frequency amplifier.-

Thelocal oscillator M is stabilized as to frequency' by a concentric line comprising an outer conductor Iii-and an inner conductor ll, which are conductively coupled together at one of their adjacent ends and 'capacitively coupled together bycapacitor 01- at their other adjacent ends. The control electrode of oscillator I4 is connected to the outer conductor lS-through the parallel combination of acondenser- I8-and a resistor l9;

The anode of oscillator M, it should be noted,

extends through a pipe 20 to the inside of inner conductor -il,-near its-end and extends, by means of a connection 2|, through the entire length of the inner conductor and thento the source of power supply +250 volts. It is preferred that the anode baby-passed to the pipe 20, as shown.

The cathode of the oscillator I4 connects with the inner'conductor ll near-its middle, while the heater element extends through a pipe 26, also to the inside of the inner conductor l1 near the middle, and then to the heater source ofsupply. The reasons forthis manner of connection may perhaps be more readily explained by comparing. the oscillator tube- 14 and the line circuit l6, ll

to the-'well-known three point Hartley oscillatorcircuit as described in United States Patent No. 1,356,763,grantedOctober 26, 1920. Such-circuit comprises an inductance whose extreme terminals arecoupled to the'anode and control electrode and whose cathode-is connectedto a point intermediate theends of the inductance. In the present case, the inner conductor 11 acts as the inductance of the Hartley circuit; audit is to the lower-end of this inductance lii-that'the anode of oscillator ld extends. The controlelectrode of oscillator I4,-it should be-noted, is connectedtothe'outer conductor which is at ground potential. Since this outer conductor i6 is conductively connected to theinner conductor, or inductance", at its other'end, we thus have a connection fromthe control electrode to the end ofinductance H which is opposite the endof the inner, conductor connected to the anode. The cathode of. -oscillator.|4,. however, extends and is effectively joined for all purposes, to the middle of the inductance l'l, since it enters the inside of inductance ll near its middle, as previously described and as shown in the drawings, In order to maintain both the cathode and the heater element of oscillator It at the same radio frequency potential, so that they fluctuate simultaneously and in the same phase with respect to one another, the heater leads are brought to the middle of the line at substantially the same location to which the cathode element is brought, and extends through the inside of inner conductor l! to the heater supply. In order to maintain the cathode and heater elements of the detector tubes l2 and I3 at the same radio frequency potential, the connections to these elements are also brought to substantially a single location on the inner conductor. for the same reasons hereinabove mentioned with respect to the identical elements of the oscillator tube, It will be noted, however, that theconnectionstothe heater and cathode elements of the. detector tubes [2 and I3 are brought to a point on the inner conductor ll near the conductively connected ends of conductors I6 and IT. This is because the cathodes of detectors l2 and I3;present an appreciable resistance load to the line circuit [6, l7, and the circuit arrangement must be such that this resistance load does. not; destroy,-to a great extent, the oscillator stability of the-tub Mproduced by the concentric lineslfi, I1. It is desired that the cathodes of the detector tubes be coupled to the inner conductor -asnearthe low potential end of the line IE, IT, in this case the conductively joined end, as, possible, but this point of connection cannot be tooclose to the low potential end for the reason that thevdetectors require an appreciable excitingyoltage to enable them to function as such, and the closer-this point ofconnection is placed toward the low potential end, the less this exciting voltage for the detector will. be. It will thus be seen that for efficient operation of the detectors, there will be a point of entrance to the innerv conductor from the cathodes of the detector tubes l2 and I3, which will not be too ,near the low potential end of the resonant line 16,- I l to interfere With the chiciency of the detectors, nor too near the high potential end of the line I6; I! to interfere with V the frequency stability of the control line circuit.

The cathodes of the detector tubes, it Will be noted,- are in circuit with groundthrougha suitable bias resistor R; Metal pipes 20, 2D and 2D" serve the useful purpose of preventing undesired capacity effects between the outer conductor l6 and the leads which extend Within the pipes, and for this reason the pipes extend slightly beyond the outer surface of the conductor I6.

Coupledto the output ofdetectors l2, 1 3 is a cascadedintermediate frequency amplifier system, comprising stages A to F, inclusive, the last stage of whichis coupled :to the. input of a diode second detector tube 22 from which the video frequencies are amplified; in: video amplifier 23 and. then ;:pass; onztoa suitable utilization circuit through a concentric coupling 24.;

For .obtaininggan; automatic gain control there is provided an electron discharge device AGC whose input, is ;coupled;tothe output of detector tube 22 andwhose output-is: coupled; through switch;-25, and connection. 26,;to the .control electrodes of several stages .of .the,intermediate.;fre-. quency amplifier The controllelectrode-of the AGC. tube is substantially at themiddle. pointof a voltage dividerqcomprisingthe 5.:meg0hm ,Ie:

of -140 volts. Since there is a positive potential of several volts, approximately 5, applied to the upper terminal of resistance 28, it will be seen that there is approximately a negative voltage of about -60 volts applied to the control electrode of tube AGO. Any change in voltage in the output of detector tube 22 will thus cause a slightly smaller change in voltage to be applied to the control electrode of tube AGC, and consequently a very much larger change in voltageappears across resistance 29 in the output of tube AGC, which great change of voltag is available for control of the intermediate frequency. amplifier stages. This is due to the fact that tube AGO functions as a direct current amplifier tube, and it should here be noted that the anode, screen and cathode electrodes are connected to a po-i tentiometer in such manner that the voltage progressively increases in positive sense with respect to the control electrode.

Where it is desired to eliminate the use of the automatic gain control circuit, switch 25 is posi- A monitor circuit comprising a tuning indi-.

cator having an amplifier detector circuit tube G, serves for enabling the operator to properly adjust the frequency of the local beat oscillator I l so that the signal carrier will fall on the mid-band frequency of the intermediate frequency amplifier. This monitor circuit is tapped to the input circuit of the line stage F of the intermediate frequency amplifier and includes as one of. its elements a sharply tuned resonant circuit 30, the oscillations from which are detected in the triode portion of the tube, G and the rectified oscillations indicated in a tuning meter 3 l A push button 28 serves to shift slightly the frequency of the resonance curve of the circuit 30 from one side of the mid-band frequency to a point symmetrically positioned on the other side of the mid-band frequency; If the receiver is properly tuned, it will be noted that the connection of the push-button 28 into the circuit will make no difference in the indication of the tuning meter 3|.

With the circuit arrangement hereinabove described and shown in the drawings, an extremely stable and satisfactory receiver was designed to function on a single frequency of 1'77 megacycles, with the local oscillator tuned to a frequency of 156 megacycles, an intermediate frequency mid-band frequency of 21 megacycles, and an intermediate frequency band pass of 3 megacycles. These figures, it is to be distinctly understood, are given by way of example only, and are not to be taken as limiting the invention.

In setting up and making test runs on the receiver, it may be desirable to supply a local signal generator which is arranged to feed cally generated oscillations over a concentric cable to a point near the receiving antenna. In this way the signal generator can be made to radiate energy into the receiving antenna which allows band width and sensitivity checks to be made on the antenna receiver combination. This set-up is provided mainly as a help in properly tuning the receiver.

It will be appreciated that the invention is not limited to the precise arrangement of parts shown and described, since various modifications may be made in the circuit elements without departing from the spirit and scope of the appended claims.

It will also be understood that the term ground used in the specification and appended claims is not limited to an actual earthed connection but includes any point of zero or relatively fixed radio frequency potential.

What is claimed is:

1. In combination, a pair of electron discharge device detectors, each having an anode, a cathode and a control electrode, said cathodes and anodes being respectively coupled together, an input circuit for applying signal energy to the control electrodes of said detectors in push-pull whereby the applied energy to one control electrode is out of phase with respect to that applied to the other, an oscillation generator stabilized as to frequency by a hollow metallic resonant circuit devoid of concentrated inductance, and means for applying the output of said generator to the cathodes of said detectors in push-push whereby the energy from said generator applied to one cathode is in phase with respect to that applied to the other cathode, said means including a circuit coupled to said resonant circuit and to the cathodes of said detectors.

2. In combination, an electron discharge device oscillation generator having an anode, a filament and a control electrode, a tuned circuit for said generator comprising inner and outer tubular conductors suitably coupled together, a connection from said anode to a source of polarizing potential, said connection extending within and substantially from one end to the other end of said inner conductor, a connection from said control electrode to said outer conductor, and connections from said filament to a source of heating energy, said last connections extending Within said inner conductor from a point near the middle of said inner conductor to said last end of said inner conductor.

3. In combination, an electron discharge device oscillation generator having an anode, cathode and control electrode, a tuned circuit for said generator comprising inner and outer tubular conductors, means for capacitively coupling said inner and outer conductors together at one end, means for conductively coupling the other end of said inner and outer conductors together, a connection from said anode to a source of potential, said connection extending within and substantially from one end to the other end of said inner conductor, a source of heating energy for said cathode, and heater leads for said cathode extending Within said inner conductor from a point near the middle of said inner conductor to the conductively coupled end of said conductors for connection to said source of heating energy, a connection from said control electrode to said outer conductor, and means for grounding said outer conductor.

4. In combination, an electron discharge device oscillation generator having an anode, a cathode, a heater element, and a control electrode, a tuned circuit for said generator comprising inner and outer tubular conductors capacitively coupled together at one end and conductively coupled together at their other end, a connection from said anode to a source of potential, said connection extending within and substantially from one end to the other end of said inner conductor, a connection from said control electrode to said outer conductor, a connection from said cathode to a point on said inner conductor near its middle, and connections from'saidheater element:to a source of heating energy,said1ast connections extending Within said inner conduc- ,9.- ;Apparatus in accordance with claim 8, in-

tor from a location adjacent said point to said :5 :cluding metallic tubular shields located between last end of said inner conductor, and meansfor grounding said outer conductor.

5. Apparatus in accordance Withclaim 4, characterized in this that said anode connectionenters said inner conductor at a point-near the capacitively coupled ends of said tubular conductors.

6. Apparatus in accordance with claimrZ, in-

cluding tubular shields located between-said inner'and outer conductors and'extending slightly;

beyond said outer conductor and insulated therefrom for accommodating and shielding the connections extending from the electrodes of said electron dischargedevice to the interior of said inner conductor.

"7. In combination, an electron discharge device oscillation generator having .an :anode, cathode and control electrode, a tuned circuitfor I said generator comprising inner and-outer tubular conductors. suitably coupled together, means;

for applying a positive potential to said anode including a'connection from said anode extending within and substantially from one end to the other end of said inner conductor, a connection from said control electrode tosaid outer con-e ductor, and heater leads for said cathode extending Within said inner conductor from apoint near th middle of said inner conductor tosaid last end of said inner conductor, ,an electron discharge device detector having electrodes, and a;

connection from one of the electrodes of said detector extending within said inner coniductor from a point near the low potential end of said inner conductor to said last end.

8. In combination, an electron discharge de-- vice oscillation generator having an anode, a cathode, a heater element, and a, controlielectrode, a tuned circuit for said generator cornprising inner and outer coaxially arranged tubular conductors oapacitively coupled together at? one end and conductively coupled together .at their other end, means for applying a suitable polarizing potential to said anode including a connection from said anode extending within and substantially from the high potential end tothe low potential end of said inner conductor, a

connection from said control electrode .to said from said cathode and heater element of said de- 1 axial conductors directly connected together from said innerand outer conductors and extending slightlyr beyond said outer conductor and insu- ;lated "from said outer conductor for accommodating-and, shielding the connections extending "from theelectrodes of said electron discharge devicesltothe interior of said inner conductor.

10.;An oscillation generator comprising an ielectron discharge device having a cathode and .apair' of coldelectrodes, a tuned oscillatory cirzcuit comprising-means having a substantially completely enclosed electromagnetic field there- 'in and being devoid of concentrated inductance,

a connection from said cathode to an eiiectively intermediate portion of said tuned circuit, and "20" -electrodesto'portions ofsaid tuned oscillatory ;circuit iwhichhave opposite polarities relative to means for inductively coupling said pair of cold said cathode.

11. An oscillation generator comprising a tuned oscillatory circuit in the form of a" pair of coa direct current standpoint at one end and -capacitively coupled together at the other end, -a-vacuum tubehavinga cathode, a grid and an substantially opposite ends of said tuned circuit, .andlaconnection from said cathode to an interanode, connections from said grid and anode to mediate portion of said tuned circuit.

12. In combination, an electron discharge device oscillation generator having an anode, a

' filament and. a control electrode, a tuned circuit for said generator comprising inner and outer tubular conductors suitably coupled together,

said elec tron discharge device being located externally of the tubular conductors of said tuned circuit, a connection from said anode to a source of polarizing potential, said connection extending Within and substantially from one end to the other end-of said inner conductor, a connection from said control electrode to said outer conductor,:and connections from said filament to a source of heating energy, said last connections extending Within said inner conductor from a point near the middle of said inner conductor to said last end of said inner conductor.

13. An oscillation generator comprising a tuned oscillatory circuit in the form of a pair of'coaxial conductors suitably coupled together and short circuited for the opera-ting frequency substantially'at one end, a vacuum tube having a cathode, a'grid and an anode, connections from said grid and anode to substantially opposite ends of said tuned circuit, and a connection from said cathode to an intermediate portion of said tuned circuit.

' BERTRAM TREVOR. 

